Apparatus and process for making paper pulp



v v 1,633,730 June 28 1 K. FISH. JR

APPARATUS ANi) PROCESS FOR MAKING PAPER PULP Filed July 11. 1925 mmvron If 11221572, J1

A TTORNEYS.

Patented June 1927.

UNITED fsTA 1 ame: mam; or shin rnAncrsco, CALHORNIA.

' arrnna'rusnnn rnocnss 'ron; Maxine-rarer. rum.

Application fled Jilly 11, 1925, Serial No.

This invention relates -to improvements in an apparatus and process for. making paper pulp.-

Heretofore vin the manufacture offpulp, p

alkah and the solvent extractivesfrom matewhen the cook is com leted. the liquor; is blown off through the atmosphereand cools and the contained volatile extractives incident to the cooking step pass off and are wasted. I

It is true in the soda and sulphate'jproe esses,-:the used liquor is saved, and. Part of it issubsequently used in the process, but before suchuse it is exposedto the air and is strengthened by the" addition of raw liquor.

Theloss of heat when the liquor'is blown off, and its consequent contact. with the air as theliquor is now recovered, renders subsequent use of-the liquor expensive, aslitis i deprivedof-the effects of the contained and intermixed volatile extractives-given ;ofl:" in the previous cook.

One of the prime objects; ofthis invention is to provide a process, and-an apparatus for carrying out the process, which will insure of the retentionof-thesolvent extractives,i.resulting from the treatment free of contact with the air and thereby preserve most of the heat and the valuesin the liquors for-future. use. Then, in the next .operation'these, liquors are enriched by the addition of strengthening agents, which produce highly important. .results and a greatly improved pulp.

A further object of the invention s the provision of an apparatus, and vprocess, for materially lightening the color of the pulp, without employing intensive bleachlng after the pulp is finished, thereby reducing t-he cost and time incident to the manufacture of the product.

Another object of the invention isto provide a step inthe process of making pulp which acts to wash the pulp before it cools, and by' the liquor used in treating the material.

Another objectofthe inventionis to provide a process, wherein, in the treatment of the material being acted upon, the digesting liquor is initially mixedwith an alkali and solvent extractives from material similar. to

' that being treated, or solvent extractives from such treated material, to soften, attack and otherwise act on the constituents of the material under treatment, other than the contained cellulose, without I weakening or dissolving said cellulose.

Other objects .and advantages will appear standing of the invention," reference is made 42,960, and in Canada membe 22, 1924.

l have found bypractical demonstration, and it is one of the objects of this discovery, that by treatingmaterial used for making ulpwith digesting liquor charged with an rial similar to thematerial being treated, and preserving this liquor free of the atmosphere, in its r'e-use', when strengthened with added alkali, or like reagent a chemical action or re-action is ,brought about, and

when the material being treated is-impreg nated with this super-charged liquorahigh gradepulpis produced. I

.A still further ob ect 7 of this invention is to provide a rocess,.where in the digesting liquoris initia ly' charged with an alkali or like reagent and solvent extractives ofplant a liquor, stronger in solvent extractivesthan the initially charged liquor first used. fromthe specific description in the specification, and will be. particularly pointed out in the claims. w

' ,In order tofobtain acomprehensive underto the accompanying :drawing which illustrates diagrammatically one' form of apparatus for carrying out the' proc S i It may bestated that .theffterm Fini'tially chargedas used in this,. application,is in tended to distinguish the liquopem'ployed,

. f roin liquorin which analkali orlike reagent is used in'wood treating processes, ;but is free of solvent extractlves at .the time said. liquor is introduced to the material being treated- In other words, Finitially charged? as herein used means that the liquor beforeactual treatment on the ma-' torial commences, contains analkali or like reagent and solvent extractives ofgplant substance. Solvent extractives as use throughout this application means substances .removed or liberated from the plant material by means of the particular-.digestingo eration and at-the temperature employed t erein. These extractives may be in the form of gases or vapour and maybe in solution or absorption-in the li uor. Thus, alkali is a solvent but not a so vent extractive as used herein. Thus a distinction between solvent 11o In the drawing, 1 illustrates a digester to receive chips or other fibrous material, suitable for making pulp. Spaced from the tank 1, is a tank 2, in which the digesting liquor is stored and pre-lieated before being introduced to digester 1, Apipe 3, connects the bottom of digester 1, withthe top of the tank 2, a valve'4, being provided to regulate the flow of fluid or volatile extractives and thelike, as the case may be, passing from tank to the digester. A pipe-2 connects the top of the dlg'ester' 1 and the top of the A ipe5, communicates with the digester 1, at or aboutthe level of the liquor, when thec-li'ips are submerged, and communicates at its other end with thebottom of tank 2,

a valve 6 bein provided to control the flow through'the pipe to tank 2.

Communicating with bottom of the di- 'gester 1 is a 7, which alsocommu'nicates with the bottom of tank 2, a valve 7 in the pipe, controllingthe flow of'liquor between the digester and tank and vice versa. In this pipe is a double acting pump 7 to assist the flowof liquor through the pipe 1n .either direction.

' At the top of the digester 1, is a closure 8, for the introduction of the chipsto be treated, and adjacent thereto is a relief valve 10. From the bottom of the digester 1, extends a drain'pipe 11,- p'rovit led with a valve 12. and adjacent thereto is a steam pipe 13, having a* valve 14, for introducing steam to the liquor in the digester l,when carrying out theiprocess.

A pipe 1 communicates with the bottom of the 'digester and connects with the suction side of a pum 1?,faiid from the opposite or outlet side of the pump leads a pipe 1, which communicates at its opposite end with the top of thedigester. This pump and pipe line is utilized to establish a circulation in the'digester 1, to facilitate the action of the liquor on and in the chips during the treating operation, as will hereinafter appear.

From the top of tank 2, extends a steam pipe 17, having a valve'lS, and adjacent thereto is a pressure release pipe 19, provided with a valve 20. The bottom of the tank 2 is provided with a pipe 21, and a valve 22. to charge the tank with liquor, and in said bottom s a draw-oil pipe 23, provided with a val-ve24, andfa steam-pipe 25, having a valve 26. v

Extending from'the top of the digester l,'is a pipe 27. having a valve 28, the pipe .27 leading to' the suction side of a vacuum pump 31, and frointhe exhaust -side of the which leads a pipe 40*," connected at its oppositeend to the bottom of the digester, and provided with a valve 40 Another pipe 43 extends from the top of tank 40 and leads to the bottom oftan'k 2, and is.

provided with a valve 44:. From the bottom of tank 40 extendsf'a pipe 45, which leads to the pump 7 and 'is' provided with a valve 46.

A pipe 41 communicates with-thetop of the'tank 40, and is provided with a valve 42. This pipe connects with the top of the digester 1, through a part of pipe 2*,and

like pipe 2 is used topass solvent ex- 'tractives and other fluids from the top of tank 40 to the top of the di ester, and vice versa, This line is only use under circum-' stances requiring passage of extractives from the tanks, should occasion require.

The top of the tank 40 is pi-ovided with a relief pipe and valve'47, and a steam "pipe and valve 48. From the bottom ofthe'tank 40, leads a pipe 49, which extends to a centri fugal machine 49, and from this machine extends a pipe 50 which leads to an evaporator 51.

In operation, digesting liquor is introduced to tank 2, through pipe 21. This liquor is. initially charged with an alkali,

such for instance as'sodium carbonate, lime, caustic potash, or the like, and solvent extractives of plant material, such for instance as the terpenes and other lighter and heavier oils. By introducing steam into tank 2, through pipe 25, the liquor is heatedto a temperature of about 274 'F.,' and a-pressure of about 30 lbs. is produced. Through the closure 8, chips to be treated are introduced to the digester 1.. Before charging the digester 1 with chips at suflicient quantity of alkali is introduced in thebottom of the digester. Then. the chips-are runinto the digester and valve 7 is partially opened to admit suflicientliquor from tank 2, to allow of saturation of the chips, and simultaneously valve 4 is partially opened to admit volatile extractives and alkali from'the totp of tank 2 to the liquor in the bottom 0 the digester, in an amount suflicient to niaintain'the desired temperature. of the chips and the liquor, carebeing taken to regulate :the heat so as to avoid raising the temperature above 150 F. Pump .1 is

started and the chargp of liquor is amped through pipe 1, tojt e top of the igester and continuously sprays the liquor. on the in the digester, which penetrates and saturates the chips and raises the temperature of the entire mass. When the digester has been charged, closure 8 is put in place, but the operation of spraying the liquor is con tmued, Valve 33 is closed and valves 28, and 32 are opened, and vacuum pump 31 is started to exhaust the air from the digester 1, to the atmosphere, through pipes 27, and 32, and a vacuum of about to inches is created.

The vacuum Withdraws the air from around the chips, and from the interiorof said chips, to render the interior more susceptible to the penetration of the digesting liquor, even the innermost cells of the individual pieces. -The vacuum is maintainedfor such length of time as may be found desirable, this depending upon the physical characteristics of the chips, and the nature and extent of treatment, the chips are to be subjected to. l

During the! time the vacuum is maintained, the pump 1 operates to continue the circulating action of the liquor. This circulation Oi the liquor in spray 'form, while the vacuum is on, insuresrthe cellular structure of the chips being further saturated withthe alkali and solvent. extractives which producesin efiecta bleaching action. While the vacuum is'on valve 4 is also kept open for continued admission of the volatile extractives to the liquor in the bottom of the .digestenlL When the material becomes thoroughly saturated the vacuum pump is stopped and valves 28 and 32 are closed, and valve 4: is opened wide to admit a full charge of the alkali and solvent ,extractives, to the digester l, to bring up the temperature of the chips toor about 212 F. The increased charge of alkali ,and solventfextractives under this higher heat removesresins and inter-cellular binding 'materials, previously softened and dissolved by the alkali and extractives under low temperature conditions and a further bleaching action of the fibers isobtained. This treatment is continued for about thirty minutes, more or less, and then valve 4 is closed.

During the vacuum period, the digesting liquor in tank 2, is heated to the desired degree, and the corresponding pressure raised in the tank by introduction of steam into the bottom of the tank through pipe 25. Y

In like manner "alve 40* may be opened if desired, to transfer volatile extractives stored in tank 40, to di gester 1. Of course, during this time the cooking liquor in tank i9 is highly heated and considerable pressure results, which causes the solvent extractives above the liquor to readily pass through pipe 4Q when valve 40* is opened. These extractives penetrate the plant material even to the inner cells of the latter,

tives, to or about 200 F. this step in the and. the chips are heated by these extracprocess requiring approximately 15 minutes.

over into the digester l,. and the chips are submerged, the level of the liquor 1n the digester being at about the level of pipe When the chips are submerged in the digester, their temperature -is about 250 F. This temperature and apressure of about fifteen pounds is produced by admitting steam to the digester through'pipe 13, and is main- 'tained for about thirty minutes, more or less, to insure of the digesting liquor conthe solvent extracti'vesl and alkali, thoroughly impregnating'the cells and fibers taining of the chi s to acton the constituents associated with the cellulose, without in any way injuryingthecellulose and the cellulosic material. To cause the most efi'eotive action of the liquor on the chips, operation of the pump 1 is continued, so that at this period in the process the super-heated iquor is circulated, which with the high heat and pressure, a uniform distribution of the liquid components in and around the chips is insured. The liquor treating step in my process is important, as the previous tre'atmentofthe plant material by the mixture of the solvent extractives and alkali ,materia-lly assists the liquor step to accomplish the desired end, bearing in mind that, previous tothis time the plant material was subjected to the 'action of the alkali and extractives, and liquor under low temperature conditions, which distributed the alkali and extractives in and throughout the cellular structure of the chips and caused a bleaching action of the fibers. The constituents to be removed have therefore, to a very large degree, been heated, softened,

dissolved, and partly removed, and the chips aremade ready for the more active treat ment of the int-'foduced digesting liquor;

The liquor serves" to melt and dissolve resins and removes same from within the chips; removes tannins and organic matter,

ltractives from chips and an alkali, lightens the color of the chips being treated a phenomena which cannot well be explained, but actual demonstration has shown it to be a fact. It is thought that the first subjection of the chips to the combined action of solvent extractives and alkali at low temperature, materially assists in the accomplishment of this hi hlyimportantresult. It is further believe that with this preliminary treatment, the subsequent treat-.

actions and reactions on the material, the cellulose. The light color of the fina product is one of therewithout afi'ectin sults flowing from my improved process and is of commercial importance as it saves the expense and delay incident to the usual intensive bleaching step. During the time the chips are treated in the digesting liquor, ebullition of the digesting liquor in the digester '1, and the liberation of the released constituents from the chips, cause certain of these constitutents to rise to the top. This layer or surface accumulation on theliquor contains resinous substances, terpenes and other by-products liberated from the chips, which would be detrimental to the, pulp if permitted to come into contact with the atmosphere and thereafter remain in or on the liquor or material, and yet these byproducts are valuable as extractives for future use, if preserved free of contact with the atmosphere. Hence, after the chips are treated with the digesting liquor in the digester 1, valve 6, in pipe 5, is opened, and pressure in the digester lblows the surface constituents accumulated on top of the liquor, and the volatile extractives above the liquor, over into tank 2, where same are preserved for use on a subsequent charge of chips in the digester. This suddenly reduces the pressure in tank 1, which causes an .outward movement of the liquor containing the constituents from the chips, pressure at this time being below the pressure in tank 1.

Valve 6, is closed, and the volatile and other constituents saved from the charge in the digester 1, are preserved in tank 2 without air in anywise coming into contact with said liquor, thus preventing oxidation or other deterioration of these important constituents. When valve 6 is closed, valve 7' .is opened, and pump 7" is started, which with the contained pressure, forces the digesting liquor from the digester 1, through pipe 7 and into the bottom of tank 2, then valve 7 is closed. H 1

In this transfer of the liquor from one tank to the other, the liberated extractives and the resinous properties taken from the wood now contained in the liquor, are car ried over without in anywise coming into contact with the atmosphere, and the orig inal digesting liquor is thereby enriched, and is preserved for a subsequent treatment, the lighter properties of course rising to the top of the liquor in tank 2, and are em-- .reaanso uents from the innermost cells of the chips and transfer same to tank 34., from whence they are transferred into tank 2 by the pump 36, and are preserved to further enrich the already enriched liquor in tank 2, to be used in a subsequent treatment. This second .vacuum treatment recovers extractives which only become volatile under pressure below atmospheric, such extractives being preserved and intermixed in the liquor for enriching same for future use.

Tank 40 is charged with cooking liquor, which may be soda, sulphate or the like, and the temperature and corresponding pressure isprovided to super-heat the liquor, the desired temperature and pressure being raised according to the character of liquor being used. While the vacuum is held in the digester 1, valves '2' and 46 are opened and steam is admitted to the top of the tank through pipe 48, which transfers the cooking liquor from tank 40 .to, the bottom of digester 1, and there valves 38 and 28 are closed, and the vacuum pump is stopped, and steam is then vadmitted to the digester through vpipc 13. The temperature of the cooking iquor in the digester is raised to about 337 F. and a corresponding pressure of about lbs. and the material is cooked from about four to seven hours, depending .upon theresult sought tobe accomplished.

Valves 7 a and 46 are of course closed as soon as the liquor has been transferred.

Durin the cooking ste the tempera ture an pressure in the igester is maintained, while the temperature and pressure in tank 40 is lowered, and periodically the valve42 or 2 are opened and the solvent volatile extractives in the digester are transferred to the top of tank 40 or tank 2 as desired and are thus saved, to enrich the liquor for future use.

During the period of the cook, the material and the liquor are agitated at intervals by introducing steam through the bottom of the digester. From time to time valve 44 may be opened and by reason of the pressure I and the pressure in the digester and the action of the pump transfers the liquor to tank 40, entirely free of contact with the atmosphere, hence saving the values in the liquor and the added solvent extractives from the material for future use.

After the cooking liquor has been transferred to tank 40, valve 7 is opened and pump 7 is started and super-heated digesting' liquor from tank 2 is transferred to the digester 1, and the pulp material is treated for approximately 30 minutes, the temperature of the liquor during this treatment being maintained at about 285 F. With a corresponding pressure, After this treatment the liquor is again transferred to tank 1 2, without in anywise coming in contact with the atmosphere. The pulp is now removed from the digester.

This treatment of the pulp material at this stage of the process acts to preliminarily wash the material, which assists in expediting the final washing of the pulp.

One of the salient features of the invention is the recovery of the cooking liquor without contact with the air to preserve the base liquor' and its now intermingled and intermixed solvent extractives for cooking the next run of chips in the digester. All this cooking liquor is not preserved asits base has been weakened by the action incurred in the digester. Hence a part of the recovered liquor is drawn off to the centrifugal machine, and treated to separate the lighter from the heavier portions, the lighter portion of the liquor being preserved to recover any remaining values. The matter separated in the centrifugal machine is removed to incinerators and treated to further recover chemicals for reuse.

As stated, the used recovered liquor in tank 40 is weakened but the materials recovered from the previous use are preserved and are utilized by adding strengthening agents to bring-it up to the desired strength for action on a charge in another reuse.

The employment of the enriched digesting liquor in tank 2, after the cooking step is completed acts'to wash the pulp material, due no doubt to the fact that it is preserved free from the atmosphere and the collected volatile extractives are retained at the temperature employed. This may be said to be a preliminary washing which of course reduces the cost and time incident to the final or usual intensive washing always necessary in the manufacture of pulp.

Another important result obtained. by my invention is, by the recovery of the volatile solvent extractives resulting from the cook,-

and transferring at least part of these to tank 2, the digesting liquor is greatly enriched for the next charge to be treated.

In order to save and utilize the volatile extractive envolved from. the evaporator, and utilize same in my method, a pipe 60 is connected to the pipe 2*, and the evaporator 51 and in the pipe is avalve 61. A condenser 62, and a. ump 63, is arranged in the pipe line 60. I collect the volatile extractives from the evaporator, the valve 61, is opened, pump 63 is started, and the extractives evolved from the contents of .theevapora-tor are pumped through the condenser and into tank 2,

to enrich the contents of the tank. Y In this stituents of the material when mixed. with water. Certain peculiar beneficial results in the treatment. ofpulp material flow from the use of super-heated liquor, and in the pres ent case advantage is taken of these results by super-heating the liquor initially charged with an alkali and solvent extractives ot the plant material. In other words, practical demonstrations have proven that by super-heating the initially charged liquor the combined temperature and pressure produces a condition, whether chemical or phy-- sical, I am unable to state, that efi'ectually treats the material to remove certain constituents from the material which may be used for subsequent use, without impairing the quality of the cellulose-- What I claim is:

1. The process of producing fibre pulp consisting in removing air from the material to be treated, treating the air free material with liquor charged with volatile extractives of plant material, and subjecting the so treated material to a second digestin operation with a renewed and strengthened liquor containing solvent extractives.

2. The process of producing strong fibre pulp consisting in removing air fipm the material to be treated, treating the air free material with liquor charged with volatile solvent extractives of plant material, and subjecting the so treated material to a second digesting operation with a renewed and strengthened liquor containing solvent extractives and preventing the atmosphere from coming into contact with the material being treated or the liquors during the successive steps of the treatments.

3. The process of producing strong fibre pup consisting in removing air from the material to betreated, treating the air free material with liquor charged with volatile solvent extractives of plant material to reen it is desired to.

- I 8. The process of move certain constituents, and subjecting the'so treated material to a second digesting operation with a stronger liquor containing solvent extractives to remove constituents which have not been removed by the previous treatment.

' 4.,The process as defined in claim 1 in which the air free material is impregnated with volatile extractivesfrom either of said liquors.

5. The process as definedin claim 1 in which the air free material is impre nated with volatile extractivesfrom said first mentioned liquor and in which excess liquor together with further volatile extractives are removed by means of a vacuum and transferred tov a liquor container.

6. The process as defined in claim 1 in which the said second mentionedliquor containing solvent extractives not removed by the first mentioned liquor is strengthened by the addition offresh pulp producing liquors.

7. The process asdefined in claim 1 further characterized in that said liquors are independently removed together with available volatile extractives to a liquor container such materials being there made available for reuse. p

producing strong fibre pulp consisting in removing air from the material to be treated,treating the air free material with liquor charged with volatile solvent extractives ofplantmaterial, and subjecting the so treated material to a second digesting operation with a previously used liquor to which the desired strengthening material has been added.

9. The process. as definedv in claim 1, wherein the so treated material is subjected to a preliminary wash with used first mentioned digesting liquor.

10. In a two-stage pulp producing process the step which consists in admixing the volatile extractives from the two treating liquors and while in a super-heated condition applyingsaid admixture to the material being treated.

11. In a two-stage pulp producing process the step which consists in enriching the liquor used in the first stage by the addition of gases or vapours evolved from the second stage liquor in the storage tank.

12. In a two stage pulp producing process the step which consists in transferring volatile extractives evolved in the digester durthe second stage cook to one or both of the tanks inwhich the treating liquors are stored.

13. An apparatus for producing pulp consisting of a digester in combination with a tank for preliminary treating liquor, a

second tank for secondary treating liquor,

a pump for removing air from material in said digester, means for circulating liquor to or fromisaid digester from or to each of said tanks, withoutcontact with the atmosphere. and separate. means for transferring vapours containing volatile solvent extractivesfrom or to the top of said digester from or to each of said tanks.

14. An apparatus as defined in claim 13 having additional means for circulating volatile extractives from the top of either or both of said tanks to the bottom of the and incorporating the recovered vapors and volatile extractives in the liquorin which the pulp is treated.

In testimony whe-reof I afiix my signature.

FREDERICK K. FISH, JR. 

